An active-matrix-type display device typically includes a TFT device that has a plurality of thin film transistor (TFT) elements, for achieving driving and light emission in units of sub-pixels. In connection with this, recently, TFT devices with a channel layer made of an oxide semiconductor are in development, for use in display devices and the like (refer to Patent Literature 1). The following describes a conventional TFT device with a channel layer made of an oxide semiconductor, with reference to FIG. 21.
The conventional TFT device illustrated in FIG. 21 includes a substrate 900. Further, the conventional TFT device includes, disposed above the substrate one on top of another in the stated order: a gate electrode 901; a gate insulating film 903; a channel layer 904; a channel protection film 906; a combination of a source electrode 907 and a drain electrode 908; and a passivation film 916. In this example, the gate insulating film 903 is composed of two layers, namely a silicon material insulating layer 9031 and an aluminum oxide layer 9032. Similarly, each of the channel protection film 906 and the passivation film 916 is a combination of an aluminum oxide layer and a silicon material insulating layer. Namely, the channel protection film 906 is composed of an aluminum oxide layer 9061 and a silicon material insulating layer 9062, and the passivation film 916 is composed of an aluminum oxide layer 9161 and a silicon material insulating layer 9162.
Further, in this example, the source electrode 907 and the drain electrode 908 are each composed of three layers, or more specifically, a Mo layer, an Al layer, and a Ti layer. Namely, the source electrode 907 is composed of a Mo layer 9071, an Al layer 9072, and a Ti layer 9073, and the drain electrode 908 is composed of a Mo layer 9081, an Al layer 9082, and a Ti layer 9083.
In the conventional TFT device illustrated in FIG. 21, due to the gate insulating film 903, the channel protection film 906, and the passivation film 916, which are located at the respective positions above or below the channel layer 904, including the aluminum oxide layers 9032, 9061, 9161 respectively, hydrogen is prevented from reaching the channel layer 904. Thus, the channel layer 904 can be prevented from being deoxidized by moisture and/or hydrogen present in the atmosphere, and further, the channel layer 904 is also prevented from losing oxygen and the like contained therein.
Meanwhile, in the conventional TFT device illustrated in FIG. 21, wiring is connected to the source electrode 907 and the drain electrode 908 via a contact hole formed in the passivation film 916.